Classical Conditioning
by GoDownWithThisShip
Summary: This fic just follows how the romantic relationship between James and Sirius grew. Lots of pranks and smooching.


**A/N:** I love this pairing so, so much, but a lot of the fanfic for it is really sad and I wanted to write something that highlights how good they are together :) So far this means pranks and smooching and some sass. But, I wanted to make sure there was 0 angst. Just 2 nerds who are crazy about each other.

They were fifteen when they first kissed. It was wet, and they fumbled awkwardly a bit, and James was so sure that he'd put Sirius off to the whole thing. But when they finally pulled back, he noticed an expression on Sirius's face that he'd never seen before. His silvery eyes were alight (but they were always that way when he broke the rules so that was nothing new) and he was biting his lower lip as if to hold back a smile. "What was that for?" he asked, his voice a quiet whisper.

They were still crammed into a stone niche, James' invisibility cloak draped over them. "What do you mean?" James countered, clumsily avoiding what had just happened between them.

"Did you just get me to come out with you tonight so that you could-"

"Don't be thick," James snapped and a loud crash from one of the rooms down the corridor interrupted him. He grinned widely at his friend, who to his relief, returned the smile. "We came out tonight to set off a few Nifflers in the trophy room. Remember?"

Sirius opened his mouth to say something, but James quickly pressed a hand over his lips. For a moment, Sirius's happy expression evaporated and he looked absolutely livid. But, a few seconds later, Filch stormed past, muttering swears under his breath.

When he passed them, Sirius let out a slow breath, and James lowered his hand. "Reckon we should go take a peek at our handiwork, then?" James suggested and Sirius nodded. The two crept along, their feet barely making a sound against the stone floor. However, they needn't have tried to be so quiet, for as they neared the trophy room, the ruckus had reached a crescendo.

Filch was screaming at the top of his lungs. Bellowing curses along with threats of what he planned to do to the students responsible. Meanwhile the small, black, mole-like creatures were scurrying around, knocking heavy, shining trophies to the floor. The over-abundance of shining things seemed to drive them absolutely mad. James and Sirius snickered as they made their way up the hall toward the staircase.

James turned to grin at his friend, but Sirius wasn't smiling. Instead, he gripped James' elbow and wrenched him closer to the wall. James followed Sirius' gaze to find the approaching form of Professor McGonagall. She was clutching a robe about her dressing gown and her hair was gathered up into a series of what appeared to be curlers. "Argus? What's that racket?" She sounded extra irritable this evening. From the look of it, the noise had woken her up.

Sirius and James inched toward the staircase at the end of the hall, keeping their backs against the cool stone wall. McGonagall whipped past them, stirring the hem of the cloak and turned abruptly into the trophy room. The two then took off at a quick run. No doubt, McGonagall would put two and two together and come looking for them.

They bounded up the stairs, taking them two at a time, no longer caring about making noise. A record, five minutes later they came skidding into view of the Fat Lady. "Dried Billywig!" James hissed and the portrait of the woman started. She yawned and stretched before squinting into the darkness.

"Whozair?" she murmured sleepily.

"Dried Billywig!" Sirius tried hopefully.

The two were afraid the Fat Lady was going to think it odd that somehow, the password was being used by someone she could not see. However, due to the lateness of the hour, she merely swung open, and James caught a glimpse of her resting her head forward into her palm and dozing off once more. They scrambled into the common room, which was mostly empty. There was only a pair of older students over by the window who were so immersed in whatever they were working on, they did not bother to look up.

On the floor by the fire, a chess set had been set up. Peter sat on one end, his face screwed up in extreme concentration. Remus laid out on the other end, lazily flipping a page in the book he held in his free hand. They both looked up when James and Sirius stumbled into the common room.

Remus opened his mouth to speak, but his friends had already began shuffling about, trying to set up the scene to look more casual. James stuffed his cloak under the sofa, and spread out on top, reaching over to snatch a stray magazine off the nearest table. Sirius on the other hand, dove to the ground and situated himself as though he had been watching the chess match in front of him for hours.

There was a tense silence that followed, which was broken by Remus. "Are you two going to explain yourselves?"

James hissed just as the portrait swung open and McGonagall clambered into the common room. Her eyes widened in surprise when she caught sight of the four of them casually lounging by the fire. She surveyed them before speaking to the older students by the window. "Have these four been here this entire time?"

They exchanged a look, obviously neither of them had even noticed the four other students but they nodded all the same. "Yes, Professor," one of them muttered.

Her eyes squinted further (James was worried she was scanning their thoughts) before turning her attention back to the Marauders. "I am hoping this is the year you boys finally learn to follow the rules. Good night." She finished her sentence by giving Remus a meaningful look before turning on her heel and marching back through the portrait hole. They murmured a dull chorus of "good night" after her.

As soon as the portrait swung shut, Peter turned on James and Sirius, his face telling them that he didn't like being left out of their shenanigans. "Where did you guys go tonight?"

Sirius shrugged, reclining back onto his elbows. "We might've taken a stroll down to the trophy room," he replied casually.

Peter's eyes were the size of mince pies. "What did you do?"

"Set off a couple Nifflers. No big deal." It was James' turn to nonchalantly answer. Peter continued to ask questions, his eyes growing wider, his laughter growing louder. It was quite expected. Remus on the other hand, was eyeing James with an expression that seemed to resemble suspicion. This was unexpected.

Finally, after thoroughly reviewing their encounter, Sirius yawned widely and got to his feet. "Bedtime for me."

"You know, my grandmother doesn't even tuck in this early," James teased and Sirius answered by flashing him a lazy middle finger as he made his way over to the dormitory stairs.

"What time is it anyway?" Peter asked.

Remus consulted the watch he wore on his left wrist. "Nearly one in the morning."

Peter squeaked and got to his feet. "Sorry, Moony. We can pick up where we left off tomorrow, yeah?" He gestured to their half-finished game of chess and Remus shrugged.

"Sure, Pete." As Peter scurried off to the dormitories, Remus sat up. James assumed he too was going to bed, but instead he turned to frown at him.

"Something's up," he said determinedly.

"Don't know what you mean," James replied truthfully.

"Running off in the middle of the night-"

"Something I've done more than half the nights we've spent here, but go on" James interjected.

Remus' frown tightened. "Yes, to nick food from the kitchens or get your hands on boot-leg Firewhiskey," he said. "But pranks like tonight's are solely a day-time event for you."

"What's your point?" James rolled his eyes.

"My point is that you need an audience, and tonight you didn't have one. So why did you do it at all?" Remus' tone wasn't accusatory at all. In fact, he was mostly just curious. But, that didn't stop the frustration from welling up inside of James.

"Sorry, _mum._ Didn't realize I'm not allowed to _leave_ my dormitory and have a bit of _fun._ "

Before Remus could answer, James was on his feet and he bent down to retrieve his cloak before striding off to the staircase. "Night," he said stiffly over his shoulder.

James had expected things to be awkward between him and Sirius, but to his relief, nothing changed. Well- nothing really. They still got up to their usual hijinks, except now they spent more time alone than with their other two friends. But, neither realized they had created a pattern that was simple to pick out if you knew what to look for. This pattern went unnoticed by most, except for their friend Remus. But, he was too tactful to say anything about it.

The pattern would begin at any time or location, although usually it took place during the evenings. Two variables were required to set everything in motion, the first being a lack of stimulation. (No homework, no new articles in Seeker Weekly, and a lack of desire to play _another_ round of exploding snap) The second was more difficult to pick up on because it was present throughout most of the day, and that would be Sirius looking bored.

These two variables would cause James to rise up quickly into a standing position and proposition his friend. (Do you wanna go see how far we can throw dung bombs off the Astronomy tower? What would happen if we hide Mrs. Norris in a suit of armor? Is there _anything_ the giant squid won't eat?)

Finally, the two would run off, perform their little tasks, and return to the common room flushed and out of breath.

This particular night found the four of them slumped around their usual sofa in the common room. "You know, just because you've finished your essays doesn't mean you're done studying," Remus said over the top of his novel. He was sitting on the floor with his back resting against the couch and his feet pointing off toward the fire.

"Speak for yourself," Sirius replied, slumped next to him. "I haven't seen you crack a text book all year."

"What can I say? I'm efficient enough to get my work done early."

Peter groaned from one of the armchairs next to the fire. "I need just another couple of inches! But, I've written everything I _know_ about the properties of Moonstones!"

"Short essay then," James teased. He was laying out on the sofa with his feet propped up on the armrest, but he sat up to look over at Peter. "Have you tried that thing I suggested where you make your handwriting really big?"

"I got into trouble for that at the end of last term." Peter shook his head. "I'm doomed."

"What about foot notes?" Sirius suggested. "I always get crazy with them. It takes up space _and_ the professor thinks you really give a damn about the topic."

"But I haven't read any other material except the textbook!" Peter brandished the text in front of them.

"You don't have to _read_ the book." Sirius rolled his eyes. "Go to the library, pick up a couple of books that are sort of related. Then you just copy down the title and author, maybe make up a couple page numbers and you're good."

Peter scrambled up and quickly shoved his work into his bag. "What time is it?"

Remus checked his watch. "Seven-thirty, Peter. Plenty of time." He also rose to his feet and looked at the other two expectantly.

"I finished bullshitting _my_ essay," Sirius said, crossing his arms over his chest. "Plus, James damn near set the place on fire last week. I think he won't be welcomed back for a bit."

Remus shot them a look, which was difficult to decipher before leading Peter out of the common room and rattling off facts Peter might have missed in his essay.

As they left, James slid down onto the floor next to Sirius who was now gazing at the logs crackling in the fire place. "What do you feel like doing tonight?" he asked. "I was thinking there might be something fun to do in the Divination class room."

Sirius nodded vaguely still watching the flames.

The next half hour found them at the foot of the spiraling stairs to the North Tower. They were both sitting on the stone floor, the invisibility cloak hiding them from prying eyes. However, it was almost not necessary as no one was wandering that part of the castle at the moment. James' hand tangled in Sirius' hair and their lips moved together slowly. James had a feeling at the bottom of his stomach that reminded him of the first time he had ridden on a proper broomstick.

Suddenly, Sirius pulled back and James let out a short breath. He found that he was being analyzed by cloudy gray eyes. "What?" he whispered, leaning forward to catch Sirius' lips again. This time Sirius leaned back and James felt a hot flush rise up his neck. "What's up?"

Sirius exhaled slowly and his gaze danced around the empty hall. He was thinking about what he was going to say, which was dangerous coming from a boy who was almost unable to stop himself from blurting out his every thought. "Look. The first couple of times, we- y'know, I figured it was just nerves or excitement or something," Sirius started and James felt his flush replaced by the iciness of dread. "Then the next few times I thought- I dunno you were probably just bored. But-"

"If you didn't want to kiss me, you should have said something," James hissed, suddenly feeling very guilty.

"When did I ever say anything about not wanting to kiss you," Sirius fired back in hushed tones. "For fuck's sake-"

"Okay, well, now that's out of the way. I think we should be kissing right now." James was grinning at him and Sirius rolled his eyes before a smile lightly pulled at his lips.

"We're having a discussion, okay? Keep your pants on!" James groaned playfully but Sirius pressed on. "I just want to know why you want to kiss me."

"Why does anyone want to kiss anybody?" James flailed his arms and nearly knocked the cloak off of them.

Sirius reached out to secure James' arms at his sides. "I really like you!" Sirius blurted out. "Okay?"

James looked at him with a puzzled expression. "Okay…and I really like you."

Sirius groaned so loudly that he awoke a portrait at the foot of the stairs. "Who's there!" the portrait called out into the darkness. James and Sirius remained very still until all was quiet again.

"I mean," Sirius explained with an expression that looked like he was slowly getting his teeth removed one by one. "I _like_ you. As in I fancy you. You bloody idiot." He added the last bit for good measure.

"And why exactly do you think I've been snogging you?" James was having trouble speaking because at the moment laughter was threatening to bubble up and spill out of his mouth.

"I dunno!" Sirius countered, barely able to keep his voice down. "For practice probably! No doubt you want to be in good form for when you _finally_ snog Evans!" The last words were marked with the unmistakable inflections of bitterness.

"Really?" James was taken aback. It was unusual to see someone so cocky and self-assured suddenly realize they might have messed up. Almost as unusual it was to see someone so self-assured and vain as Sirius Black question another person's attraction. "Use your head! When's the last time I even mentioned her name?"

Sirius had to think about the question, because _wow_ James hadn't so much as mentioned Evans for…Merlin it had to be a record. "Dunno," Sirius mumbled. "Couple of months probably."

"And what happened a couple of months ago?"

Sirius didn't have to think about the question, because he knew the answer immediately. "You kissed me." He paused. "So what?"

"So!" James said at normal volume. Sirius shushed him quickly and James remembered himself and continued in a whisper. "So I fancy _you,_ you bloody idiot!"

Before he could say anything more, James was silenced by Sirius' lips on his once more. This time, more feverish and electric. Sirius' hand was on his jaw, and he allowed himself to be pulled closer. Sirius' tongue slipped between his lips and James gasped into his mouth. As they fumbled under the cloak, they didn't pick up on the faint sounds of footsteps coming down from the tower.

"H-hello?" an uncertain voice called in the darkness and the two pulled away from each other to see Professor Fraxinus was standing at the bottom of the stairs, just a foot away from the two. They were both breathing as quietly as possible as she squinted into the darkness. The tip of her short wand was alight and she held it aloft. Her other arm clutched a copy of the Evening Prophet to her body. The expression on her face was strained and almost pained.

A few moments later she bustled away and Sirius laughed quietly in James' ear. "Reckon she's run to the loo then. Judging by the newspaper and the look on her face, I'd say we've got some time." Professor Fraxinus' bowel troubles were well known, and the poor woman had been known to disappear from classes on occasion.

"Why doesn't she just go up in the tower?"James muttered as the two of them began climbing the steps.

"Reckon it's the smell," Sirius replied, cringing at the thought.

As the two of them climbed up through the trap door (Sirius' handy knife unlocking the latch for them) James quickly muttered _Lumos_. The dusty room would have been spacious, if it didn't appear as though someone had tried to shove as much furniture inside as possible. Squat tables, velvet ottomans, and lush pillows were strewn about and it gave the place the very distinct feeling of a yard sale.

"So, where do we start?" Sirius asked, striding into the room and fishing his own wand from his pocket.

James made his way over to a cabinet on the other side of the room displaying a variety of china. "Wanna mess up someone's tea leaf readings?"

Sirius made his way over, sliding around tables and snatched a couple of cups off the shelf. "How badly do you think a fourth year would shit themselves if they looked into their cup and saw the Grim?" He made his way over to an ancient side table situated next to a squashy arm chair in the front of the room. It sported a cup of brightly colored spare quills and he carefully selected two of them.

The boys settled at one of the squat tables, their legs tangling together underneath it and began their work. James had picked up a bottle of long-lasting ink from Hogsmeade a couple of weekends ago for an event such as this. He fished it out of his pocket and set it on the table in front of them. The two quietly doodled at the bottom of the cups for a few moments. Sirius finally held up his cup to James' face with a flourish. "Whaddya think?" The jagged outline of what James thought looked like a blob stared at him from the pit of the cup.

"Looks good," he lied, grinning at his friend. A few moments later he held his cup up for Sirius to inspect.

Sirius let out a loud bark of laughter and clutched his sides. James' grin widened and he cleared his throat before mimicking Professor Fraxinus' airy voice. "My dear, what is it that you see?"

Sirius grabbed the cup from James' hands and turned it over in his hands, screwing up his face as though he were in deep concentration. "I-I see, a-" he lowered his voice and looked at James, his eyes wide in a fake expression of surprise. "A willy, professor!" The two roared with laughter and quieted down quickly as they heard the latch on the trapdoor click.

With reflexes born from his time spent in the Quidditch pitch, James snatched up his ink and got up to replace the cups on the shelf. "Well, that was quick," Sirius muttered from behind him and he fished the cloak from the pocket of his robes and threw it about the two of them, vanishing them from sight just as Professor Fraxinus appeared.

They inched away from the cabinet and pressed themselves against the wall beside it. The elderly woman looked much more serene than when they had seen her earlier that night. She eyed the quills left out on the table and looked around before muttering something about people not cleaning up after themselves. She made her way over to the table and plucked them up and as she was putting them in their proper place, James and Sirius slipped from the room.


End file.
